This invention relates to covers for truck beds, and more particularly to a rebalancing valve for a truck cover sliding pivot.
Many trucks, particularly those hauling loose loads such as sand and gravel, need a truck cover to prevent the wind from blowing load particles off the load bed. Various apparatus have been devised for covering a truck load. Some such apparatus include a motor for selectively winding a flexible cover. My U.S. Pat. No. 5,031,955 provides a truck cover which may be conveniently motor operated from the cab of a truck while simultaneously extending the cover over the truck bed and pressing down on the front of the cover proximate a winding assembly which winds up the cover at the front of the truck bed. Similarly, U.S. Pat. No. 5,238,287 shows a front mount telescopic arm truck cover system, and U.S. Pat. No. 5,524,953 shows a contractable vehicle bed cover assembly with an extendable closure.
Container trucks, however, present special problems. In particular, such container trucks tend to have differently sized beds, and are required to accept containers of different dimensions. To accommodate these variances, the arms normally used in conventional truck bed covers have to be long enough to reach from their mounting point to both the front and rear ends of the truck bed. U.S. Pat. No. 5,292,169 shows such a truck container cover. Not only do such arms require great effort to move from either their forwardmost or rearwardmost position, but they are not able to efficiently accommodate containers of different sizes.
U.S. Pat. No. 5,752,735 shows one attempt to address at least this latter problem with adjustable pivot points shifted along opposite rails by hydraulic cylinders.
The present invention is a hydraulic circuit comprising first and second cylinders, and a piston disposed in each of the cylinders. A pump communicates with one side of one of the pistons, and a pressure relief valve has a position wherein the pump communicates with another side of the one piston and with the other piston. This circuit is particularly applicable to covers for trucks with cylinders disposed on opposite sides of the truck.
Accordingly, an object of this invention is to provide a truck cover that requires a smaller clearance than conventional truck covers.
Still another object of this invention is to provide a truck cover that is suitable for use with container trucks.
Still another object of this invention is to provide a truck cover bow that has adjustable pivots.
Still another object of this invention is to provide a hydraulic circuit of the type described above which rebalances the force applied to adjust the pivots.
These and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in conjunction with the accompanying drawings.